Close control thermostat



. 1, 1931. E. BLETZ CLOSE CbNTROL THERMOSTAT Filed Dec. 19, 1930 INVENTOR Edward Blefz WITNESSES ATTORNEY Patented Dec. 1, 1931 UNITED STATES PATENT OFFICE.

nnwnnn BLETZ, or Lnxmerou, onro, ASSIGNOR 'ro wns'rmenoosn nnncrnio &

' murac'ruame comrmr, A CORPORATION or rnnnsrnvmm cLosn I coN'rnoL rrrmtmosra'r Application filed December 19, 1930. Serial No. 503,437. I

ential of operation.

In practicing my invention, 1 provide a snap-acting disc of the general kind disclosed and claimed. in Patent No. 1,448,240

to J. A. Spencer, with thermally-actuable 'means for shifting the position of the mounting of the disc relatively to its base.

In the single sheet of drawings: Figure 1 is a view, partially in side elevation and partially in section, of a device. embodying my invention,

Fig. 2 is a view, partially inside elevation and partially in vertical section, through a .modified form of device embodying my invention,

Fig. 3 is a bottom plan view of the device shown in Fig. 1,

t Fig. 4 is a sectional view of the device embodying my invention taken on the line IVIV of Fig. 3, and

Fig. 5 is a bottom plan view of the base of a device embodying my invention, the disc being removed.

Referring first to Fig. 1 of the drawings,

- I have there illustrated a substantially cir cular base assembl 11 which may be of substantially the-kin disclosed and claimed in Patent No. 1,697,886 to J. A. Spencer, including, more particularly, one or more metal discs 12 and a disc 13 of electric-insulating material, such as mica, secured'against its outer face, and four fixed terminal and con tact members 14, 16,- 17 and 18 which are suitably secured against the outer surface of the mica sheet 13 by a plurality of insulated rivets 19. 1

.The sheet of mica 13 and the 12 of metal are securedtogether by a tubular rivet 21 which extends beyond the inner face of the base in order to constitute a guide.

A pair of rods 22 and 23 have correspondcentral stud 32, a portion of which'moves within the tubular rivet 21,the disc 28 being loosely supported on the stud or rod 32. At its upperend, the rod 32 is provided with screw threads for receiving a plurality of adjusting nuts 33, 34 and 36.

Cooperating bimetallic discs 37 and 38 are strung on the rods32 immediately above the tubular rivet 21 and between it and nut 33 which is out of engagement with the uppermost disc 38 at room temperatures. The discs 37 and 38 have the high-expansion compo nent located on the outside of the dished disc so that, upon temperature increase of the disc,

it will bow in such manner as to increase the depth or the amount of dish thereof. v,

Between nut 34 and cross-bar 24, similar sets of dished bimetallic discs 41 and 42 are provided, exceptthat the low-expansion component thereof is on the outside of the dished disc and the high-expansion component is on its inside. 4 v

A stop 43 is provided, in the form of an adjustable screw extending through cross bar 26 and normally out of engagement with the upper end of stud 32.

Referring to Fig. 2 of the drawings, I have there shown a device similar to that shown in Fig. 1 of the drawings, except that a spring "44 is utilized instead of the dished bimetal discs 41 and 42.' In all other respects, the device is the same as was described in connection with Fig; 1 of the drawings.

Stop screws 46 extend through the disc 28 and into the base 12 in order that it may be possible to vary the value of the other op-= erating temperature, as will be hereinafter set forth. 1

drawings, the initial adjustment is made by turning nut 36 to such an extent, as to eflect an initial engagement between contact-br1dgingmembers 31 and the fixed terminal membars on the base. "Nut 34 is then turned toward nut 36, and bar 24 and nut 33 are adjusted to substantially the positions shown in thedrawings. It is obvious that it is impossible to give dimensions in inches, as the operating characs 1'5 42 may, and will, vary and also the desired teristics of disc 28 and of discs 37 38, 41 and operating temperature values may be differ- The operation of the device is substantially as follows: upon an increase of thetemperature of the ambient air or other material surrounding the device, the snap-acting. disc 28 will undergo slow initial deformation which,

if the temperature change is continued, will ;ultimately cause it to snap ozer into the oppositely, dished shape, The discs 41 and 42 which are not snap-acting, will contract, and

discs 37 and38 will expand so that the uppermost disc 38 will engagenut 33 and cause axial movement oflstud 32 Axial movement of-stud 32 will ,gause a decreased dishing of bimetal disc 28, thereby varying its operating characteristic at its upper limit of operation. That is, as the disc 28 is flattened, not only by the effect of its two components because of the'variation or temperature thereof but also by the increased flattening caused by the floating support, the disc 28 will snap over sooner, that is, at a lower temperaturmthan would be the case otherwise.

If it is desired to greatly reduce this upper temperature limit of operation, the nut 33 will be moved'close to the u permost disc 38,. and screw; 43will be moved away from the end of stud 32. If, however, it is not desired to greatly reduce the temperature difl'erential of operation, screw 43 willbe initially set with a small gap between itsend and the adjacent end of stud 32, and 'nut 33 will be disc 38.

If it be assumed that the disc 28 has been actuated to its opposed dishedshape, and that the temperature nowde'creases, the discs 37 and 38 will flatten, and the discs41 and 42 will increase in depth, thereby forcing the stud 32 downwardly and, as the stop screws 46 operate to limit the dish of disc28'in the other direction, it will be evident thatthe disc 28 will snap back to the position shown in the drawings at a higher temperature than I would otherwise be the case.

It is obvious that I may use a single metal spring 44instead of the discs 41 and 42 and member thereon.

eration.

Various modifications may be made in my invention without departing from the s irit and scope thereof, and I desire, there ore, that only such limitations shall be placed thereon as are imposed by the prior art or are set, forth in the appended claims.

I claim as my invention:

- 1. In 'athermal switch including a base, contact. members thereon, a snap-acting bimetal disc andcontact members thereon cooperating with the contact members on the base, a thermally-controlled floating supporting means for said disc. I

2. In a thermal switch including a base, a contact member thereon, a snap-acting bimetal discnormally having a relatively large temperature difi'erential of operation, and a contact member on said disc cooperating with the contact member on the base, a thermallycontrolled floating supportingmeans for the di'sc to reduce the temperature differential of tion from one extreme position to another, means for reducing the temperature differen- ,tial of the bimetal disc, said means including temperature differential between its operaa thermally-actuable floating support for the bimetal disc effective to vary the position of the disc relatively to the base and the contact In testimony whereof, Ihave hereunto subscribed my name this 26. day of November,

1930.- e EDWARD BLETZ. 

